中文摘要：

利用模拟降雨试验，采用2个雨强（1.5 mm min-1，2.0 mm min-1），4个坡度（10°，15°，20°，25°），对杨凌塿土细沟发育的特征及其坡面流速分布规律进行了研究。结果表明，坡度增加会造成细沟溯源侵蚀及下切侵蚀的加剧，但随着坡度的增加，总侵蚀量的增幅趋于平缓，暗示可能存在坡面侵蚀量由强转弱的临界坡度。坡度与各侵蚀指标间均表现出极显著的相关性，说明坡度是影响细沟发育的主要因素，细沟侵蚀量与总侵蚀量也表现为极显著的相关性，相关系数高达0.97，说明坡面侵蚀加剧主要由细沟侵蚀引起。坡面流速、细沟间及细沟流速与距坡顶距离有较好的正相关关系，雨强增加会加剧这种趋势的波动性，同时坡度对坡面、细沟间及细沟流速的影响不大，且各流速间也没有明显的大小关系，这与一般认为的细沟流速高于细沟间流速的观点不同，这也是今后试验过程中需要进一步验证的部分。

英文摘要：

A field experiment was carried in Yangling using simulated rainfalls, designed to have two rainfall intensities （1.5 and 2.0mm min-1）, on slopes of Lou soil, different in gradient （10°,15°,20° and 25°）, to study characteristics of rill development and distribution of flow velocity along the slopes. Results show that slope gradient is positively related to rill density and average depth of the rills, but with the increase in slope gradient, the increment of total erosion rate tends to level off in amplitude, which implies that there is likely a threshold slope gradient where soil erosion begins to turn from strong into weak. Slope gradient shows extremely significant relationship with to the various indices of soil erosion, indicating that slope gradient is the major factor affecting development of rills. Rill erosion rate is also found to be closely related to total erosion rate, with correlation coefficient being 0.97, indicating that the aggravation of soil erosion on the slope is caused mainly by rill erosion. Flow velocities on the slope, in and in-between rills are all positively related to their distances to the slope top. Rainfall intensity intensifies fluctuation of the trend. However, slope gradient does not have much influence on flow velocities on slopes, in and in-between rills and, moreover, no significant relationship is found between these flows in velocity, which is contradictory to the general conclusion that flow velocity is higher in rills than in-between rills, and remains to be further verified in future experiments.